Nicole Bidoit

Fixpoint Calculus for Querying Semistructured Data

The paper proposes two query languages for semistructured data G-Fixpoint and G-While whose expressive power is comparable to Fixpoint and While respectively. These languages are multi-sorted like logic languages integrating fixpoint path expressions.

Implicit Temporal Query Languages: Towards Completeness

In the propositional case, it is known that temporal logic (TL) and first order logic with timestamp(TS-FO) have the same expressive power. Recent work has proved that, in contrast, there are first order logic queries on timestampda tabases that are not expressible in first order temporal logic: TL is not complete. Specifying a complete implicit temporal query language remains an open problem. We investigate two extensions of TL, namely NTL and RNTL. A strict hierarchy in expressive power among fragments RNTLi of RNTL is established. On the one hand, it leads to the conjecture that RNTL is complete. On the other hand, it provides a new promising perspective towards proving the well-known conjecture that there is a strict hierarchy among the i time-variable fragments TS-FOi of TS-FO.

A Family of Nested Query Languages for Semi-structured Data

Semi-structured data are commonly represented by labelled graphs. The labels may be strings, integers, . . . Thus their type is atomic. They are carried by edges and/or nodes. In this paper, we investigate a nested graph representation of semi-structured data. Some nodes of our graphs may be labelled by graphs. Our motivation is to bring the data model in use closer to the natural presentation of data, in particular closer to the Web presentation. The main purpose of the paper is to provide query languages of reasonable expressive power for querying nested db-graphs.